在Python中解析用户提供的数学公式的安全方法
Python是否有数学表达式解析器+计算器 我不是第一个问这个问题的人，但答案通常指向在Python中解析用户提供的数学公式的安全方法,python,Python,Python是否有数学表达式解析器+计算器 我不是第一个问这个问题的人，但答案通常指向eval（）。例如，可以这样做： >>> safe_list = ['math','acos', 'asin', 'atan', 'atan2', 'ceil', 'cos', 'cosh', 'degrees', 'e', 'exp', 'fabs', 'floor', 'fmod', 'frexp', 'hypot', 'ldexp', 'log', 'log10', 'modf', 'p
eval（）>>> safe_list = ['math','acos', 'asin', 'atan', 'atan2', 'ceil', 'cos', 'cosh', 'degrees', 'e', 'exp', 'fabs', 'floor', 'fmod', 'frexp', 'hypot', 'ldexp', 'log', 'log10', 'modf', 'pi', 'pow', 'radians', 'sin', 'sinh', 'sqrt', 'tan', 'tanh', 'abs']
>>> safe_dict = dict([ (k, locals().get(k, None)) for k in safe_list ])
>>> s = "2+3"
>>> eval(s, {"__builtins__":None}, safe_dict)
5
evaleval>>> import MathParser
>>> m=MathParser.PyMathParser()
>>> m.expression = s_badbaduser
>>> m.evaluate();
Segmentation fault
将pyp解析导入为pyp
输入数学
进口经营者
类NumericStringParser（对象）：
'''
大部分代码来自fourFn.py解析示例
http://pyparsing.wikispaces.com/file/view/fourFn.py
http://pyparsing.wikispaces.com/message/view/home/15549426
__作者保罗·麦奎尔
我所做的只是将Paul McGuire的fourFn.py重写为一个类，这样我就可以使用它了
在其他地方更容易。
'''
def推送优先（自身、strg、loc、toks）：
self.exprStack.append（toks[0]）
def pushUMinus（自身、strg、loc、toks）：
如果toks和toks[0]='-'：
self.exprStack.append（'unary-'）
定义初始化（自）：
"""
expop:：“^”
multop:：“*”|“/”
addop:：“+”|“-”
整数：：['+'|'-']'0'..'9'+
原子：：π| E | real | fn'（'expr'）'|'（'expr'）'
因子：：原子[expop因子]*
术语：：因子[多顶因子]*
expr:：term[addop term]*
"""
point=pyp.Literal（“.”）
e=pyp.无案例横向（“e”）
fnumber=pyp.Combine（pyp.Word（“+-”+pyp.nums，pyp.nums）+
pyp.Optional（point+pyp.Optional（pyp.Word（pyp.nums）））+
pyp.Optional（e+pyp.Word（“+-”+pyp.nums，pyp.nums）））
ident=pyp.Word（pyp.alphas，pyp.alphas+pyp.nums+“$”）
plus=pyp.Literal（“+”）
减=pyp.Literal（“-”）
mult=pyp.Literal（“*”）
div=pyp.Literal（“/”）
lpar=pyp.Literal（“”.suppress（）
rpar=pyp.Literal（“”）。suppress（）
addop=正|负
multop=mult | div
expop=pyp.Literal（“^”）
pi=pyp.无案例横向（“pi”）
expr=pyp.Forward（）
atom=（（pyp.Optional（pyp.oneOf（“-+”））+
（pi | e | fnumber | ident+lpar+expr+rpar）.setParseAction（self.pushFirst））
|pyp.Optional（pyp.oneOf（“-+”））+pyp.Group（lpar+expr+rpar）
).setParseAction（self.pushumius）
#通过将指数定义为“原子[^factor]…”而不是
#“atom[^atom]…”，我们得到的是从右到左的指数，而不是从左到右的指数
#也就是说，2^3^2=2^（3^2），而不是（2^3）^2。
因子=pyp.Forward（）
因子ε和（（a>0）-（a<0））或0}
self.exprStack=[]
def评估测试包（自身）：
op=s.pop（）
如果op==“一元-”：
返回-自我评估测试包
如果在“+-*/^”中有op：
op2=自我评估测试包
op1=自我评估测试包
返回self.opn[op]（op1，op2）
elif op==“PI”：
返回math.pi#3.1415926535
elif op==“E”：
返回math.e#2.718281828
elif op在self.fn中：
返回self.fn[op]（self.evaluateStack）
elif op[0]。isalpha（）：
返回0
其他：
返回浮动（op）
def eval（self，num_字符串，parseAll=True）：
self.exprStack=[]
结果=self.bnf.parseString（num_字符串，parseAll）
val=self.evaluateStack（self.exprStack[：]）
返回值
nsp=NumericStringParser（）
打印（nsp.eval（'1+2'））
# 3.0
打印（nsp.eval（'2*3-5'））
# 1.0
tree = ast.parse(s, mode='eval')
valid = all(isinstance(node, whitelist) for node in ast.walk(tree))
if valid:
result = eval(compile(tree, filename='', mode='eval'),
{"__builtins__": None}, safe_dict)
whitelist = (ast.Expression, ast.Call, ast.Name, ast.Load,
ast.BinOp, ast.UnaryOp, ast.operator, ast.unaryop, ast.cmpop,
ast.Num,
)
我在这里建立了几个帖子来创建一个评估类。也用 我基本上把它重写成一个类对象
import sys
import ast
import operator as op
import abc
import math
class IEvaluator:
__metaclass__ = abc.ABCMeta
@abc.abstractmethod
def eval_expr(cls, expr, subs): # @NoSelf
'''IMPORTANT: this is class method, overload it with @classmethod!
Evaluate an expression given in the expr string.
:param expr: str. String expression.
:param subs: dict. Dictionary with values to substitute.
:returns: Evaluated expression result.
'''
class Evaluator(IEvaluator):
'''Generic evaluator for a string expression. Uses ast and operator
modules. The expr string is parsed with ast resulting in a node tree.
Then the node tree is recursively traversed and evaluated with operations
from the operator module.
:implements: IEvaluator
'''
@classmethod
def _get_op(cls, node):
'''Get the operator corresponding to the node.
:param node: Operator node type with node.op property.
'''
# supported operators
operators = {
ast.Add: op.add,
ast.Sub: op.sub,
ast.Mult: op.mul,
ast.Div: op.truediv,
ast.Pow: op.pow,
ast.BitXor: op.xor,
ast.USub: op.neg
}
return operators[type(node.op)]
@classmethod
def _get_op_fun(cls, node):
# fun_call = {'sin': math.sin, 'cos': math.cos}[node.func.id]
fun_call = getattr(math, node.func.id)
return fun_call
@classmethod
def _num_op(cls, node, subs):
'''Return the value of the node.
:param node: Value node type with node.n property.
'''
return node.n
@classmethod
def _bin_op(cls, node, subs):
'''Eval the left and right nodes, and call the binary operator.
:param node: Binary operator with node.op, node.left, and node.right
properties.
'''
op = cls._get_op(node)
left_node = cls.eval(node.left, subs)
right_node = cls.eval(node.right, subs)
return op(left_node, right_node)
@classmethod
def _unary_op(cls, node, subs):
'''Eval the node operand and call the unary operator.
:param node: Unary operator with node.op and node.operand properties.
'''
op = cls._get_op(node)
return op(cls.eval(node.operand, subs))
@classmethod
def _subs_op(cls, node, subs):
'''Return the value of the variable represented by the node.
:param node: Name node with node.id property to identify the variable.
'''
try:
return subs[node.id]
except KeyError:
raise TypeError(node)
@classmethod
def _call_op(cls, node, subs):
arg_list = []
for node_arg in node.args:
arg_list.append(cls.eval(node_arg, subs))
fun_call = cls._get_op_fun(node)
return fun_call(*arg_list)
@classmethod
def eval(cls, node, subs):
'''The node is actually a tree. The node type i.e. type(node) is:
ast.Num, ast.BinOp, ast.UnaryOp or ast.Name.
Depending on the node type the node will have the following properties:
node.n - Nodes value.
node.id - Node id corresponding to a key in the subs dictionary.
node.op - operation node. Type of node.op identifies the operation.
type(node.op) is one of ast.Add, ast.Sub, ast.Mult, ast.Div,
ast.Pow, ast.BitXor, or ast.USub.
node.left or node.right - Binary operation node needs to have links
to left and right nodes.
node.operand - Unary operation node needs to have an operand.
The binary and unary operations call eval recursively.
'''
# The functional logic is:
# if isinstance(node, ast.Num): # <number>
# return node.n
# elif isinstance(node, ast.BinOp): # <left> <operator> <right>
# return operators[type(node.op)](eval_(node.left, subs),
# eval_(node.right, subs))
# elif isinstance(node, ast.UnaryOp): # <operator> <operand> e.g., -1
# return operators[type(node.op)](eval_(node.operand, subs))
# else:
# try:
# return subs[node.id]
# except KeyError:
# raise TypeError(node)
node_type = type(node)
return {
# Value in the expression. Leaf.
ast.Num: cls._num_op, # <number>
# Bin operation with two operands.
ast.BinOp: cls._bin_op, # <left> <operator> <right>
# Unary operation such as neg.
ast.UnaryOp: cls._unary_op, # <operator> <operand> e.g., -1
# Sub the value for the variable. Leaf.
ast.Name: cls._subs_op, # <variable>
ast.Call: cls._call_op
}[node_type](node, subs)
@classmethod
def eval_expr(cls, expr, subs=None):
'''Evaluates a string expression. The expr string is parsed with ast
resulting in a node tree. Then the eval method is used to recursively
traverse and evaluate the nodes. Symbolic params are taken from subs.
:Example:
>>> eval_expr('2^6')
4
>>> eval_expr('2**6')
64
>>> eval_expr('1 + 2*3**(4^5) / (6 + -7)')
-5.0
>>> eval_expr('x + y', {'x': 1, 'y': 2})
3
:param expr: str. String expression.
:param subs: dict. (default: globals of current and calling stack.)
:returns: Result of running the evaluator.
:implements: IEvaluator.eval_expr
'''
# ref: https://stackoverflow.com/a/9558001/3457624
if subs is None:
# Get the globals
frame = sys._getframe()
subs = {}
subs.update(frame.f_globals)
if frame.f_back:
subs.update(frame.f_back.f_globals)
expr_tree = ast.parse(expr, mode='eval').body
return cls.eval(expr_tree, subs)
2*x - y**2
(x, y): (1, 2)
2*x - y**2 = -2
subs: {'y': 2, 'x': 1}
2*x - y**2 = -2
sin_subs: {'y': 2, 'x': 1}
sin(log10(x*y)) = 0.296504042171
查看上的一个类似问题，我看到了这个问题，但执行用户提供的代码（无论如何保护）对我来说似乎不安全。上面的例子只是为了说明保护
eval函数代码（lambda:0）。\uuuu class\uuuuuuuuuuuuuuuuuu和（lambda:0）.func\u代码。\uuuuu class\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu>分别感谢联合国大学，这看起来很完美！代码看起来不错！如何替换Python3中最好的cmp（a，0）
呢？@riddlegical:为了Python3的兼容性，@SinanErdem:不限制数字的大小（比如说，如果操作仅仅是加法，那么可能会限制得太多），您可以在一段时间内运行nsp.eval
。您可能还想知道进程可以使用什么。这部分代码直接来自。我猜是选择了将解析器弯曲到世界上大多数人使用的语法，而不是将世界上大多数人弯曲到Python使用的语法。这是一个很好的技巧！我仍然更喜欢unutbu的解决方案，因为它在设计上是安全的，但这是一个很好的技巧-我想这将使eval
更加安全。谢谢这种方法无法防止像9**9**9**9**9**9**9
这样的字符串试图
import sys
import ast
import operator as op
import abc
import math
class IEvaluator:
__metaclass__ = abc.ABCMeta
@abc.abstractmethod
def eval_expr(cls, expr, subs): # @NoSelf
'''IMPORTANT: this is class method, overload it with @classmethod!
Evaluate an expression given in the expr string.
:param expr: str. String expression.
:param subs: dict. Dictionary with values to substitute.
:returns: Evaluated expression result.
'''
class Evaluator(IEvaluator):
'''Generic evaluator for a string expression. Uses ast and operator
modules. The expr string is parsed with ast resulting in a node tree.
Then the node tree is recursively traversed and evaluated with operations
from the operator module.
:implements: IEvaluator
'''
@classmethod
def _get_op(cls, node):
'''Get the operator corresponding to the node.
:param node: Operator node type with node.op property.
'''
# supported operators
operators = {
ast.Add: op.add,
ast.Sub: op.sub,
ast.Mult: op.mul,
ast.Div: op.truediv,
ast.Pow: op.pow,
ast.BitXor: op.xor,
ast.USub: op.neg
}
return operators[type(node.op)]
@classmethod
def _get_op_fun(cls, node):
# fun_call = {'sin': math.sin, 'cos': math.cos}[node.func.id]
fun_call = getattr(math, node.func.id)
return fun_call
@classmethod
def _num_op(cls, node, subs):
'''Return the value of the node.
:param node: Value node type with node.n property.
'''
return node.n
@classmethod
def _bin_op(cls, node, subs):
'''Eval the left and right nodes, and call the binary operator.
:param node: Binary operator with node.op, node.left, and node.right
properties.
'''
op = cls._get_op(node)
left_node = cls.eval(node.left, subs)
right_node = cls.eval(node.right, subs)
return op(left_node, right_node)
@classmethod
def _unary_op(cls, node, subs):
'''Eval the node operand and call the unary operator.
:param node: Unary operator with node.op and node.operand properties.
'''
op = cls._get_op(node)
return op(cls.eval(node.operand, subs))
@classmethod
def _subs_op(cls, node, subs):
'''Return the value of the variable represented by the node.
:param node: Name node with node.id property to identify the variable.
'''
try:
return subs[node.id]
except KeyError:
raise TypeError(node)
@classmethod
def _call_op(cls, node, subs):
arg_list = []
for node_arg in node.args:
arg_list.append(cls.eval(node_arg, subs))
fun_call = cls._get_op_fun(node)
return fun_call(*arg_list)
@classmethod
def eval(cls, node, subs):
'''The node is actually a tree. The node type i.e. type(node) is:
ast.Num, ast.BinOp, ast.UnaryOp or ast.Name.
Depending on the node type the node will have the following properties:
node.n - Nodes value.
node.id - Node id corresponding to a key in the subs dictionary.
node.op - operation node. Type of node.op identifies the operation.
type(node.op) is one of ast.Add, ast.Sub, ast.Mult, ast.Div,
ast.Pow, ast.BitXor, or ast.USub.
node.left or node.right - Binary operation node needs to have links
to left and right nodes.
node.operand - Unary operation node needs to have an operand.
The binary and unary operations call eval recursively.
'''
# The functional logic is:
# if isinstance(node, ast.Num): # <number>
# return node.n
# elif isinstance(node, ast.BinOp): # <left> <operator> <right>
# return operators[type(node.op)](eval_(node.left, subs),
# eval_(node.right, subs))
# elif isinstance(node, ast.UnaryOp): # <operator> <operand> e.g., -1
# return operators[type(node.op)](eval_(node.operand, subs))
# else:
# try:
# return subs[node.id]
# except KeyError:
# raise TypeError(node)
node_type = type(node)
return {
# Value in the expression. Leaf.
ast.Num: cls._num_op, # <number>
# Bin operation with two operands.
ast.BinOp: cls._bin_op, # <left> <operator> <right>
# Unary operation such as neg.
ast.UnaryOp: cls._unary_op, # <operator> <operand> e.g., -1
# Sub the value for the variable. Leaf.
ast.Name: cls._subs_op, # <variable>
ast.Call: cls._call_op
}[node_type](node, subs)
@classmethod
def eval_expr(cls, expr, subs=None):
'''Evaluates a string expression. The expr string is parsed with ast
resulting in a node tree. Then the eval method is used to recursively
traverse and evaluate the nodes. Symbolic params are taken from subs.
:Example:
>>> eval_expr('2^6')
4
>>> eval_expr('2**6')
64
>>> eval_expr('1 + 2*3**(4^5) / (6 + -7)')
-5.0
>>> eval_expr('x + y', {'x': 1, 'y': 2})
3
:param expr: str. String expression.
:param subs: dict. (default: globals of current and calling stack.)
:returns: Result of running the evaluator.
:implements: IEvaluator.eval_expr
'''
# ref: https://stackoverflow.com/a/9558001/3457624
if subs is None:
# Get the globals
frame = sys._getframe()
subs = {}
subs.update(frame.f_globals)
if frame.f_back:
subs.update(frame.f_back.f_globals)
expr_tree = ast.parse(expr, mode='eval').body
return cls.eval(expr_tree, subs)
import sympy
from eval_sympy import Evaluator
# test case...
x = sympy.Symbol('x')
y = sympy.Symbol('y')
expr = x * 2 - y ** 2
# z = expr.subs({x:1, y:2})
str_expr = str(expr)
print str_expr
x = 1
y = 2
out0 = Evaluator.eval_expr(str_expr)
print '(x, y): ({}, {})'.format(x, y)
print str_expr, ' = ', out0
subs1 = {'x': 1, 'y': 2}
out1 = Evaluator.eval_expr(str_expr, subs1)
print 'subs: ', subs1
print str_expr, ' = ', out1
sin_subs = {'x': 1, 'y': 2}
sin_out = Evaluator.eval_expr('sin(log10(x*y))', sin_subs)
print 'sin_subs: ', sin_subs
print 'sin(log10(x*y)) = ', sin_out
2*x - y**2
(x, y): (1, 2)
2*x - y**2 = -2
subs: {'y': 2, 'x': 1}
2*x - y**2 = -2
sin_subs: {'y': 2, 'x': 1}
sin(log10(x*y)) = 0.296504042171